VLBA Observations of Strong Anisotripic Radio Scattering Toward the Orion Nebula
Kounkel, Marina; Rodríguez, Luis F.; Loinard, Laurent; Briceño, Cesar; Hartmann, Lee; Ortiz-León, Gisela N.; Mioduszewski, Amy J.; Torres, Rosa M.; Johnson, Michael D.
United States, Mexico, Germany, Chile
Abstract
We present observations of VLBA 20, a radio source found toward the edge of the Orion Nebula Cluster (ONC). Nonthermal emission dominates the spectral energy distribution of this object from the radio to mid-infrared regime, suggesting that VLBA 20 is extragalactic. This source is heavily scattered in the radio regime. Very Long Baseline Array observations resolve it to ∼34 × 19 mas at 5 GHz, and the wavelength dependence of the scattering disk is consistent with ν -2 at other frequencies. The origin of the scattering is most likely the ionized X-ray emitting gas from the winds of the most massive stars of the ONC. The scattering is highly anisotropic, with the axis ratio of 2:1, higher than what is typically observed toward other sources.